Acceleration sensors or accelerometers are mass products in automotive and consumer goods electronics. Therefore, example systems are desired that integrate a simple threshold (value) switch or a threshold detector in an Application Specific Integrated Circuit (ASIC). Such a system may be, for example, a Tire Pressure Monitoring System (TPMS)-sensor.
Migrating or converting the systems into new or smaller technology nodes is challenging, since a complexity of the Complementary Metal Oxide Semiconductor (CMOS)-processes shall not be unnecessarily increased and an existing integration scheme of the CMOS circuit shall be maintained with lowest possible developmental efforts.
For technologies using 130 nm process technologies and below, considering, for example, a topology of the frontend-of-line-structures is important. They should not exceed a total thickness of a few hundred nanometers to not influence a typically used boro-phosphate-silicate-glass (BPSG) polishing step. However, accelerometers, for example, are formed with a mounting technology using a thick polycrystalline layer. Furthermore, a reduction to a lowest possible amount of additional steps and a shared use of available or present processes is advantageous for a successful integration.
A further challenge is the interaction of housing and sensor. In capacitive sensors, capacitor elements are, according to the type of housing, exposed to substantial or significant stress. Therefore, special housings are often used, which contribute a considerable cost component of the overall or entire system.
Furthermore, other suggestions exist of how to implement an integrated structure in a substrate. They are either very expensive or difficult to integrate them in a CMOS-process. Moreover, many of today's available capacitive working structures are extremely vulnerable against stress impact from a packet.
Therefore, there is a need for an improved approach.